Find the sum S9 of the first 9 terms of the geometric sequence 2, 2.4, 2.88, …
Sequences & series worksheet with answers
1.Easy
a₁ = 2r = 1.2n = 9
S9 =
2.Easy
Find the sum S6 of the first 6 terms of the geometric sequence 1, 2, 4, …
a₁ = 1r = 2n = 6
S6 =
3.Medium
Apply the ratio test to Σk=1∞ 2ᵏ·k!/kᵏ. Find L = lim |ak+1/ak|.
ak = 2ᵏ·k!/kᵏ
L =
4.Medium
Exactly one of the four series diverges. Click it.
A: Σ (2/5)ᵏB: Σ k!/3ᵏC: Σ 1/k²D: Σ 1/(3ᵏ + k)
- 1A: Σ (2/5)ᵏ
- 2B: Σ k!/3ᵏ
- 3C: Σ 1/k²
- 4D: Σ 1/(3ᵏ + k)
5.Hard
f(x) = eˣ is approximated by its Maclaurin polynomial of degree 3 at x = 0.5. Use the Lagrange error bound M·|x|ⁿ⁺¹/(n + 1)! with M = e0.5 = 1.649 to find the largest possible error |R₃|.
f(x) = eˣn = 3x = 0.5M = 1.649
|R₃| =
6.Hard
Use the Maclaurin polynomial of degree 4 of f(x) = cos(3x) to approximate f(−0.5). Give P₄(−0.5).
f(x) = cos(3x)n = 4x = −0.5
P₄(−0.5) =
Answer key
- 1. S9 = 41.6
- 2. S6 = 63
- 3. L = 0.7358
- 4. B: Σ k!/3ᵏ
- 5. |R₃| = 0.004294
- 6. P₄(−0.5) = 0.08594
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